...and the gperf being used no longer emits "register" in C++ code.

Unlike Clang with -Wdynamic-exception-spec ignored, at least GCC 7.2
-std=gnu++17 always makes dynamic exception specs hard errors, which would cause
errors both when building StaticLibrary_libcmis and when including
libcmis/libcmis.hxx in ucb/source/ucp/cmis/.  So patch away all dynamic
exception specifications from all external/libcmis include files indirectly
included via libcmis/libcmis.hxx, and (to silence the remaining dynamic
exception specifications in the innards of external/libcmis, which I did not
feel like also patching away) build StaticLibrary_libcmis as C++03 if necessary,
and wait for upstream libcmis to eventually be ported to C++17.

And external/firebird needs to be built with CXXFLAGS_CXX11 (which amounts to
C++17 with this patch) since 9206a08a "Upgrade
to ICU 60.1", so the relevant dynamic exception specifications had to be patched
away from its innards.

Change-Id: I3a0c9ec83c7c1d413559459631970f69ab977f31
Reviewed-on: https://gerrit.libreoffice.org/43851Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>